Are House MD hallucinations self induced or a product of his Vicodin usage?

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Now I'm not all knowing on Vicodin usage, so I'm not sure if prolonged use (8 years plus) can cause hallucinations. If you go back to season 4 finally, Wilson's Heart (part one and two), you watch the episode where Amber dies. During this finally, House does a number of Self Treatments where he Over Doses on Alzheimer's medication, undergoes direct electro shock therapy to his brain, and other radical "experiments". Watch here: http://tvshack.net/tv/House/season_4/episode_15/ If you've watched season 5, you'll notice that House's entire team agrees that his mental instability is a product of Vicodin. In Season 6 his hallucinations are all gone (the writers make you believe it's because he's "off" Vicodin, but you can also assume it's because of his intense psychotherapy treatment). What says you? Did he do it to himself the day Amber died, or is it a product of Vicodin?